Glycomimetics as decorating motifs for oligonucleotides: solid-phase synthesis, stability, and hybridization properties of carbopeptoid-oligonucleotide conjugates

The online solid-phase synthesis of oligonucleotides conjugated at the 3' end with [1-6]-linked oligosaccharide mimics having the O-glycosidic linkages replaced by amide bonds is here described. The assembly of the carbohydrate domain has been carried out by exploiting classical solid phase peptide synthetic protocols, starting from solid supports functionalized with 1-azido sugars, in association with suitably protected 1-azido uronic acids of glucose and lactose, chosen as model addition monomers. After the insertion of a flexible linker, elongation of the oligodeoxyribonucleotide (ODN) chain was performed by standard automated phosphoramidite protocols. 3'-Glycoconjugated 18-mers exhibited an increased enzymatic stability with respect to the same unmodified ODN sequence. UV thermal denaturation experiments showed that the presence of the oligosaccharide tail at the 3' end of the oligonucleotides did not negatively interfere with their duplex formation abilities.